Magnetic recording head, including a device for adjusting the gap width



July 24, 1951 o. G. c. HARE 2,561,365

MAGNETIC RECORDING HEAD, INCLUDING A DEVICE FOR ADJUSTING THE GAP WIDTH Filed May e, 1948 INVENTOR DONALD G. C. HARE ORN Patented July 24, 1951 MAGNETIC RECORDING HEAD, INCLUDING A DEVICE FOR ADJUSTING THE GAP WIDTH Donald G. C. Hare, Stamford, Conn., assignor to Magnetic Equipment, Inc., Greenwich, Conn., a corporation of Delaware Application May 6, 1948, Serial No. 25,480

The present invention relates to magnetic sound recording and reproducing systems and more particularly to recording and reproducing systems employing magnetic tape as the signal carrier. The invention comprises an improved transducing device or head for such systems that is simple of construction, is easy of assembly, insuresuniform but not excessive pressure between the laminations of the core and permits of ready adjustment of the head mounting.

A particular feature of the head construction of the invention is that it is adapted for rapid and exact adjustment of the width of the gap between the pole faces after assembly of the parts and after mounting of the head.

A further important feature of the new head construction is that it insures against undesired separation of the halves of the core.

Other features of the invention will become apparent as the description proceeds.

In the accompanying drawing:

Fig. 1 is an exploded view of a head embodying the invention, the coils being omitted for clary;

Fig. 2 is a top plan view, partly broken away, of the assembled head; and

Fig. 3 is a vertical sectional view taken on the line 33 of Fig. 2.

The construction of the new head can best be understood from the exploded view of Fig. 1 to which reference may now be had. The head comprises two like mounting pieces 2 and 4 of brass or the like, a spacer 6, also of brass or the like, and a metal core of desired characteristics formed in two sections, 8 and ID. A suitable base I2, of aluminum or the like, and an insulating cover plate [4 carrying terminals It for the windings completes the assembly.

The mounting pieces 2 and 4 are centrally apertured, as indicated at [8, for reception of a mounting screw 20 (see Figs. 2 and 3) and are cut away medially at opposite ends, as indicated at spacings 22 and 24, to provide spaced branches or furcations 26 and 28 at opposite sides of the openings 22 and 24 respectively, branches 26 being somewhat larger than branches 28.

The top mounting piece 4 has a pair of counterbored passages 30 drilled therethrough adjacent the inner ends of the spacings 22 and 24, respectively, and lower mounting piece 2 has a pair of threaded holes 32 therein, each of which, when the parts are assembled, is in alignment with one of the passages 30 in the upper mounting piece 4. Each branch 26 and 28 of the pieces 2 and 4 is provided with a. small hole 34 there-.

8 Claims. (01. 1'79-1 00.2)

through, the holes all having smooth bores and the respective holes in the two pieces being in alignment when the head is assembled. The pairs of branches 26 of the mounting pieces 2 and 4 are provided with means for varying the spacing therebetween, said means comprising a threaded hole 36 in one branch 26 of each pair extending from the spacing 22 transversely through the section, a smooth bored passage 38 in the other branch 26 of each pair, in substantial alignment with hole 36 and preferably coun terbored at its outer end, and a small screw 40 disposed in the passage 38 and across the spacing 22 and threaded into the hole 36. Similarly, a small screw 42, positioned in passage 44 in one branch 28 of each mounting piece and across the spacing 24 and threaded into an aligned hole 46 in the other branch 28, serves to adjust the spacing between the branches 28 of each pair. The split construction of the non-magnetic mounting pieces 2 and 4 permits the branches of each pair of branches 26 and 28 to yield elastically and to be moved toward and away from each other by adjustment of the screws 40 and 42 respectively, the limited amount of movement necessary for such adjustment not exceeding the elastic limit of the material.

The spacing member 6 comprises a cylindrical member which is turned down at its ends for insertion into the holes 18 of the mounting pieces 2 and 4 and which is axially drilled for reception of the screw or bolt 20.

The core, as heretofore indicated, is made of two parts 8 and [0. Each part is composed of a plurality of laminations of soft iron, Mumetal, or the like which are stacked one above the other on pins 48 and 50 which pass through aligned holes in the laminations. The laminations are substantially C-shaped with a tapered end 5| and a straight end 52, the tapered'ends 5| forming the pole pieces of the core and defining the gap for flux linkage with the magnetic signal carrier.

In assembling the new head, the laminations of each part 8 and ll] of the core are first assembled on the pins 48 and 50, and the assembly is then suitably impregnated with varnish or the like. While the two halves of the core are held together in a suitable jig, the meeting edges, both at the poles 5| and at the ends 52, are lapped and the outer surface of the core is polished. After removal fromthe jig, a winding 6| (not shown in Fig. 1) is formed on each core part between the pins 48 .and 50. The spacer 6 andthe core parts 8 and 10 with the windings thereon are then mounted on the piece 2, with the tapered ends 5| adjacent branches 26 and the straight ends 52 adjacent branches 28, by insertion of a reduced end of the spacer in the hole I8 and of the ends of the pins 48 and 50 in the holes 34, with which they are adapted to coincide. After addition to the assembly of the upper mounting piece 4, the holes 34 of which coincide with the other ends of the pins 48 and 50 and fit thereover, the screws 54 are inserted through the passages 3.0, threaded into the holes 32 and tightened until the mount-. ing pieces are held in firm engagement with the spacer 6. Preferably the length of the central portion of the spacer 6 is slightly greater than the depth of the core parts to avoid excessive pressure on the core when the screws 54 are tightened. After the parts have been thus as sembled, the core parts are brought into close contact by tightening of the screws 42 in the branches 28 of both mounting pieces. The gap between the pole faces may be initially adjusted at this time to any desired value by adjustment of the screws 40 in sections 26.

The assembled head is then positioned on the base II, the cover I4 is positioned on the head and the whole is secured to a suitable platform or panel 56 by means of the bolt or screw 20. The terminal wires of the coils 6| are brought out and connected to the terminals 16 on the cover l4. Preferably, as shown, the cover I4 is provided with ports 58 for access to the screws 54 and base part II is suitably recessed, as indicated at 6,0, to provide clearance for the ends of the screws 54. Preferably screws 40, 42 and 54 and pins 48 and 50 are made of a steel or other material having a coefficient of expansion substantially equal to that of the core.

In Fig. 2, in which the assembled head, with the cover broken away, is shown in plan view, and in Fig. 3, in which a sectional view of the assembled head is shown, the magnetic tape which spans the gap between the pole faces and is employed as a signal carrier is indicated at 59 and the windings of the coil are represented at 6|.

With the above described construction, the edges of the laminations of each half of the core, respectively, are kept flush with each other by the pins 48 and 50, and the core as a whole is kept under uniform pressure by the screws 54. Due to the split construction of the mounting pieces 2 and 4 and to the provision of the adjusting screws 40 and 42, the gap between the pole faces 5! may be adjusted at any time for desired flux linkage with the magnetic tape 59 and the pressure between the ends 52 can be increased or decreased as desired. The orientation of the head with respect to the magnetic tape can be readily effected by turning the assembly as a whole on the screw 20. The forwardly extending branches 26 of the mounting pieces 2 and 4 serve as convenient guide means for the magnetic tape 59 as it travels over the gap between the pole pieces.

The invention has now been described with reference to one specific embodiment thereof. Obviously various changes could be made in the shape and construction of the various parts of the new head without departing from the scope of the invention as defined in the appended claims.

The following is claimed:

1. A transducing device for magnetic tape sound systems comprising a core having a winding thereon and formed of two like parts in engagement along one end and spaced apart at the other end to provide a, gap for flux linkage with magnetic tape, a supporting framework for said core including two spaced element each having two oppositely disposed pairs of furcations, each pair defining an open ended slot therebetween, the slots in one element being aligned with the slots in the other element, means holding said core parts between said elements with the engaged ends of the core parts aligned with one pair of slots and the gap between the pole pieces aligned with the other pair of slot the pairs of furcations forming the slots aligned with the gap between the pole faces extending beyond the core parts to provide therewith an accurate record guide and means for adjusting the width of said slots.

2. The combination with a magnetic sound head of the type wherein the pole faces of a two part coil carrying laminated core define a gap for flux linkage with magnetic tape, of a nonmagnetic support structure for the core comprising two plate elements spaced for reception of the core. therebetween each having a pair of forcetions at one end defining therebetween an open ended slot substantially aligned with the gap be? tween the pole faces of the core and a second pair of furcations at the other end defining therebetween an open ended slot substantially aligned with the junction of the core parts, pins extending through said plate members and the laminations of the core, said first pair of furcations of each ofsaid plate element extending beyond the core to provide therewith an accurate record guide and means associated with said plate elements for ad-. justing the width of each of said slots.

3. The combination according to claim 1 wherein said head includes a spacing member substantially axiallyv disposed within the core and adapted to be engaged by said plate elements and screw means for holding said elements in engagement with said spacing member, whereby said plate elements can be rigidly held together without undue pressure on the laminations ofthe core.

4. The combination according to claim 1 wherein said last mentioned means and said pins are of material having substantially the same coefiiv cient of expansion as the core.

5. The combination according to claim 1 where-J in said last mentioned means of said claim comprises screws interconnecting the furcations of each pair.

6. The combination with a magnetic sound head of the type wherein the pole faces of a coil care rying laminated core are separated by a gap for flux linkage with magnetic tape, of a support structure for the core comprising a pair of spaced elements engaging the outer laminations of the core, means rigidly securing the elements and core together, said elements each having a pair of furcations defining therebetween an open ended slot, the gap between the pole faces of the core being disposed between said slots, said furcations or each element extending beyond the core to pro-i vide therewith an accurate record guide and means associated with said elements for inde-. pendently adjusting the width of said slots where.-. by the gap can be precisely adjusted for uniform width.

7. A precision sound head for magnetic tape reproducing devices comprising two C-shaped laminated core parts, one end only of each part being tapered to provide a pole face of lesser area than the cross-sectional area of the core part for concentrating magnetic flux in magnetic tape bridging a gap between thetapered end of the core parts, coils surrounding said core parts, two plate elements spaced for reception therebetween of the core parts and the coils carried thereby, each plate element being formed with a pair of furcations at its opposite ends, each pair defining an open ended slot, each plate element being of a single piece of non-magnetic material having sufllcient resilience to permit the furcations on opposite sides of the slots to be moved toward and away from each other, the slots of one plate element being aligned with the slots of the other plate element, pins extending through said plate elements and said core parts for mounting said core parts between said plate elements with the tapered ends of the core parts separated by a gap aligned with a slot of each plate member and the other ends of the core parts terminating in a zone aligned with the other slot of each plate element, the pairs of furcations forming the slots aligned with the gap between the pole faces extending beyond the core parts to provide therewith an accurate record guide and means carried by the furcations of plate element for independently adjusting the width of each slot for adjustment of the spacing between the 1ike ends of the core parts.

8. A transducing head adapted for cooperation with a magnetic carrier which comprises a core having a winding thereon and formed of two like parts spaced apart at least at one end to provide a gap for flux interlinkage with a magnetic carrier, a supporting framework for said core including two spaced elements each having two pairs of 'furcations, each pair defining an open ended slot therebetween, the slots in one element being aligned with the slots in the other element, means REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,044,033 Von Heising June 16, 1936 2,058,399 Begun Oct. 27, 1935 2,351,003 Camras June 12, 1944 2,351,007 Camras June 13, 1944 2,360,625 Walker Oct. 17, 1944 2,446,624 Allison Aug. 10, 1948 2,483,123 Clapp Sept. 27, 1949 

